Summary of Work: The scope of this work is to elucidate the molecular mechanisms that give rise to the induced expression of the v-Ha- ras transgene in Tg.AC mice. Our approach in this work is to successufully accomplish three goals. The first goal is to obtain a molecular mechanistic understanding of the role GATA-3 (a 40 kd zinc finger transcription factor known to bind to the transgene promoter) plays in both normal skin and tumor development. Expression constructs and transgenic mice altered in their expression pattern for gata-3 have been developed and are under study. Also, GATA promoted lacZ transgenic mice developmented in the labotratory of James Douglas Engel at Northwestern have been procured and should provide valuable information about GATA-3 role in both tumorigenesis and skin development. The second major goal of the laboratory is the identification of transcription factors and their respective cis binding sites on the actively transcribed v- HA-ras promoter. DNase I footprint experiments comparing the occupied regions of the actively transcribed transgene versus the inactive gene are ongoing. Given that most factors and their sites have been identified in the globin system (the transgene has a zetaglobin promoter) a comparison should identify other factors essential to the induced response and reguired for tumorigensis. The last approach is to obtain the chromosomal regions surronding the transgene. Given that only one of five of the transgenic founders displayed a skin tumorigenic phenotype it is likely that the site of integration is important. In a collaborative effort we are using the TAR technique, developed in Mike Resnick's laboratory to clone the chromsomal regions that flank Tg.AC's transgene. Identification of regions required for Tg.AC's tumorigenic response will be essential. In addition to this work we will continue to work with other scientist in our laboratory to exploit the reliability of Tg.ACs tumorigenic response both with regard to the time and location to identify genetic and epigenetic changes important for the tumorigenic process.